This invention relates generally to devices for forming voids within propellant grains, and, more particularly, to devices for forming voids after the grain has cured.
In order to improve burning characteristics of propellant grains, a variety of uniquely shaped voids are positioned in the grains. Voids amenable to extrusion or casting, such as stars, require no further shaping, but other shapes require elaborate machines in order to cut the voids into the grains. For example, a grain with a longitudinal cylindrical cavity may require a conical slot. In the past, this conical slot was machined into the grain with a vertical lathe having special cutters.
The use of a conventional lathe entailed the problems of transporting and positioning of the grain in the lathe. Grains of considerable weight magnify these problems, of course. Further, detailed setup procedures are required in the use of a conventional lathe. The time consumed in transporting, positioning, and setting up are essentially equal whether one cut or numerous cuts are involved. Thus, for example, only one slotting operation in the grain becomes very inefficient with the above lathe.
These drawbacks have motivated the search for alternative devices such as a slotting fixture that minimizes the time per operation of each grain.